Rotary gear pump



Feb. 14, 967 NOBUO MORITA ROTARY GEAR PUMP 3 Sheets-Sheet l Filed Aug. 5, 1966 INVENTOR Feb. 14, 1967 NOBUO MORITA 3,303,793

ROTARY GEAR PUMP Filed Aug. 51966 5 Sheets-Sheec 2 INVENTOR Feb 14, i967 Nouo MORITA 3,3%793 ROTARY GEAR PUMP Filed Aug. 5, 1966 I5 Sheets-Sheet 5 ma/M INVENTOR United States Patent O 3,303,793 RGTARY GEAR PUMP Nobuo Morita, 535 Kawachimachi, Hiraoka, Japan Filed Aug. 5, 1966, Ser. No. 570,539 Claims priority, application Japan, Aug. 17, 1965, #l/50,248 1 Claim. (Cl. 163-126) The present invention relates to a rotary gear pump of the kind that a pair of rotors arranged in an inscribed relation are kept oil-tight with a pair of discs in the both sides and with a pair of blocks in the circumference by the application of its own delivery pressure, in order to protect the sliding members from uneven wearing and check the reverse ow of liquid from delivery to suction side so as to improve the volume eiciency of pump in high pressure delivery.

It is of known practice in rotary gear pumps for feeding pressure oil to hydraulic system that manufacturing tolerances and gear profiles are taken as major factors to minimize the wearing loss and pocketing phenomenon so as to improve the volume eiciency of pump. Rotary gear pumps of known practice are however impossible to maintain suiciently high volume eiiiciency over a long period in high pressure delivery where the clearances around the rotors are an important factor to determine the volume efficiency of pump.

In a conventional type of rotary gear pump as shown in FIGS. S and 9, sectioned vertically in the former and taken on the W-W line in the latter, an outer rotor 31 and an inner rotor 30 inscribed in it are rotating in a slidingly engaged relation with each other in a casing 23 and cover 29 with a suction port 32 and a delivery port 33 opening at either side of rotors 39 and 31. In such a mechanism of rotary gear pump, both the rotors 30 and 31 are given positive reactions Fd due to delivery pressure and negative reactions Fs due to suction pressure in quite an unbalanced manner not only to wear sliding members of pump unevenly but also to place excessive bending stress on the shaft 34. The uneven wear of sliding members will naturally enlarge the circumferential clearances of rotors so as to increase the reverse ow of liquid from delivery to suction side and therefore to decrease the volume eiciency of pump. The excessive bending stress on shaft will naturally lower the mechanical eiciency of pump.

The above-described disadvantages of conventional rotary gear pumps are overcome by the present invention, which will be more apparent from the following description of a preferred form of embodiment shown by way of example in the accompanying FIGS. 1 to 7.

FIG. 1 is a vertical section of a rotary gear pump in accordance with the invention.

FIG. 2 is a horizontal section taken on the line X--X in FIG. 1.

FIG. 3 is an enlarged plan view showing the rotors and port ring of gear pump in FIG. 1.

FIG. 4 is a vertical section of FIG. 3.

FG. 5 illustrates a balance of reactions acting on the discs shown in FIG. 2.

FIG. 6 is the cross-sectional detail along Y-Y line of FIG. 1.

FIG. 7 is a vertical section taken on the line Z-Z in FIG. 2.

The embodiment of the invention comprises a casing 1 provided radially with a suction port 6 and a delivery port 7, a cover 2 closing the casing 1 rmly, a shaft 3 supported rotatably in the casing 1 and the cover 2, an inner rotor 4 fixed on the shaft 3, an outer rotor 5 engaging with the inner rotor 4 in an inscribingly slidable relation, a pair of discs 10, embracing the outer rotor 4 and inner rotor 5 in a slidable relation at the both sides 3,303,793v Patented Feb. 14, 1967 of the rotors 4 and 5, a pair of annular spaces 24, 24 respectively provided on the casing 1 and on the cover 2 in contact with the discs 10, 10, a port ring 9 embracing the outer rotor 5 at the circumference of rotor 5 with oil wings 11 and 12 respectively extending in the suction and in the delivery side around the rotor 5, and a pair of blocks 17, 17 with stems 16, 16 being in a slidably contact with the outer rotor 5 respectively at the top and at the bottom of rotor 5. The outer rotor 5 is provided with a plurality of radial pores 8 each at a corner to connect the inside and the outside of the rotor 5. Each of the annular spaces 24, 24 is margined by a pair of annular grooves with O-ring packings 22, 23 in them in a manner that one of the annular grooves is inside the other in such an eccentricv relation as to have wider space between them in the delivery side of pump than in the suction side of it. The port ring 9 is provided with a pair of narrow apertures 13, 13 respectively at the top and at the bottom of it, each between the oil wings 11 and 12 in a normal direction to them. Each narrow aperture 13 is formed integrally with a wide aperture 14 in the radial direction of rotor 5 so as to guide slidably the block 17 in the wide aperture 14 and the stem 16 in the narrow aperture 13. The oil wing 12 in the delivery side of pump is connected to the narrow aperture 13, 13 by way of canals 15, 15. The oil wing 11 in the suction side of pump is provided with an endless groove 18 along the inner edge. The endless groove 13 is provided with a gasket packing 19. Each of discs 10, 10 is provided with a pore 25 to connect the delivery side of rotors 4, 5 to the annular spaces 24, 24 through it. The port ring 9 is supported by pins 21, 21 received in pin holes 20, 20 provided in the casing 1 and the cover 2.

In the operation of rotary gear pump in accordance with the invention, positive reactions Fd due to delivery pressure and negative reactions Fs due to suction pressure are acted to the inner walls of discs 10, 10, and, at the same time, reactions F1 and F2 are acted to the outer walls of discs 10, 10 inwardly due to the pressure raised in the annular spaces 24, 24 where system oil is filled from the delivery side of rotors 4, 5 by way of the pores 25, 25. The discs 10, 1t) therefore receive inward even forces F which are resultants of the reactions Fd partly cancelled by F2 and the reactions Fs partly added by F1, as illustratively shown in FIG. 5. Thus the rotors 4 and 5 are given a same inward pressure evenly all over the both sides in contact with the discs 1i), 10. Meanwhile, the blocks 17, 17 are put into a sufiiciently oiltight contact with the cricumference of outer rotor 5 by means of the stems 16, 16 which is pressed inwardly by system oil applied to the ends of stems 16, 16 in the narrow apertures 13, 13 from the oil Wing 12 in the delivery side of pump by way of canals 15, 15. Thus the delivery side clearance 27 is definitely closed to the suction side clearance 26 around the circumference of outer rotor 5.

So far described, the rotary gear pump in accordance with the invention has the clearances closed sufficiently oil-tight with its own delivery pressure by means of the discs 1l), 1li and blocks 17, 17 at the both sides and around the circumference of rotors 4, 5. The oil-tightness of discs 1l), 10 and blocks 17, 17 is automatically controlled by the delivery pressure of pump, in other words, always kept at the optimum to the operation. It will thus be seen that the rotary gear pump in accordance with the invention has the sliding members protected suiiciently from uneven wearing and the reverse flow or leakage of liquid checked reliably from delivery to suction side so as to improve both 'the volume and the mechanical efciency of pump in response to the pressure working In the delivery side.

What is claimed is:

A rotary gear pump comprising a casing provided radially with a suction port and 4a delivery port, a cover closing said casing firmly, a shaft supported rotatably in said casing and said cover, an inner rotor iXed on said shaft, and outer rotor engaging with said inner rotor in an inscribingly slidable relation, a pair of discs embracing said outer rotor and said inner rotor in a slidable relation at the both sides of said rotors, a pair of annular spaces respectively provided on said casing and said cover in contact with said discs, a port ring embracing said outer rotor at the circumference of said outer rotor with oil wings respectively extending in the suction and in the delivery side around said outer rotor, and a pair of blocks with stems being in a slidable contact with said outer rotor respectively at the top and at the bottom of said outer rotor, said port ring being provided with a pair of narrow apertures respectively at the top and at the bottom thereof, each positioned between said oil wings in a normal direction to said oil wings and formed integrally with a wide aperture in the radial direction of said outer rotor so as to guide each of said blocks and stems therein, said annular spaces and said wide apertures being connected to the delivery side of said rotors, whereby said discs and said blocks are put into a contact with said rotors with even tightness in response to the pressure working in said delivery side.

References Cited by the Examiner UNITED STATES PATENTS 1,700,818 2/1929 Wilsey 103-126 1,964,330 6/1934 Pitt 103-126 2,458,958 1/1949 Pigott et al. 103-126 2,657,638 11/1953 English 103-126 2,915,982 12/1959 Crandall 103-126 2,925,044 2/1960 Brundage 103-126 3,106,897 10/1963 Johnson 103-126 DONLEY I. STOCKING, Primaly Examiner.

W. I. GOODLIN, Assistant Examiner. 

